1. Field of the Invention
This invention relates to: (a) a method for preparing tar-depleted liquid smoke from a tar-containing aqueous liquid smoke solution, (b) a tar-depleted smoke colored and flavored tubular food casing, (c) a tar-depleted aqueous liquid smoke solution with smoke color, odor and flavor capability, and (d) a method for preparing smoke colored and smoke flavored encased foodstuff.
2. Description of the Prior Art
Tubular cellulosic food casings are used extensively for processing a great variety of meat products and other food items. The food casings are generally thin-walled tubing of various diameters prepared from reconstituted materials, such as regenerated cellulose. Cellulosic food casings may also be prepared with fibrous webs embedded in the wall thereof, such casings commonly being referred to as "fibrous food casings."
The many different recipes and modes of processing that are used by the processed food industry to suit different tastes, and even regional preferences, generally necessitate the use of food casings with a variety of characteristics. In some instances, for example, food casings are required to have multifunctional uses wherein they serve as containers during the processing of a food product encased therein, and then also serve as a protective wrapping for the finished product. In the processed meat industry, however, the food casings used in the preparation of many types of meat products, such as various types of sausages, such as frankfurters, bolognas and the like, beef rolls, hams and the like, are frequently removed from about the processed meat product prior to slicing and/or final packaging.
Surface appearance and flavor are important factors in the commercial and consumer acceptance of processed meat products, and a common feature of most varieties of such products involves the use of "smoking" for imparting characteristic flavor and color thereto. The "smoking" of food products is generally accomplished by the food processor subjecting the food product to actual contact with smoke in a gaseous or cloud-like form. Such "smoking" processes, however, have not been considered completely satisfactory for a variety of reasons, including the inefficiencies and lack of uniformity of the "smoking" operation. Because of the shortcomings experienced, many meat packers now employ various types of liquid aqueous solutions of wood-derived smoke constituents, commonly called "liquid smoke solutions" that have been developed and used commercially by the food processor in the processing of many types of meat and other food products. For convenience in this specification, the as-purchased "liquid smoke solution" will be frequently referred to as "as-is" liquid smoke.
The application of "liquid smoke solutions" to meat products is generally carried out in a variety of ways, including spraying or dipping an encased food product during the processing thereof, or by incorporating the "liquid smoke solution" in the recipe itself. The actual operation of "smoking" by spraying or dipping is not completely satisfactory due to inability to treat the encased product uniformly, and incorporation of "liquid smoke solutions" in the meat recipe does not always provide the desired surface appearance because of dilution of smoke ingredients. Incorporation in the recipe also reduces the stability of the meat emulsion, and will adversely affect taste if high concentrations are used. Application of liquid smoke to encased food products by the food processor, such as by spraying or dipping, also causes unwanted pollution and equipment corrosion problems for the food processor. In addition, encased sausages treated by application of the liquid smoke during commercial processing have been found to yield, afer peeling the casing from the treated encased food product, sausages which are lacking in smoke color uniformity from sausage to sausage, and from batch of sausages to batch of sausages. What is even more undesirable is the lack of uniformity of coloration which often appears on the surface of the same sausage, including light and dark streaks, light and dark blotches, and even uncolored spots which especially appear at the ends of sausages.
It has also been suggested, as for example disclosed in U.S. Pat. No. 3,330,669 to Hollenbeck, that application of a viscous liquid smoke solution to the inside surface of a deshirred tubular food casing by the food processor immediately prior to stuffing the casing with a sausage emulsion, results in preparation of processed food products that exhibit acceptable color and smoky flavor after cooking and removal of the casing. However, the Hollenbeck procedure has not been found practical and is not used commercially. The viscous liquid smoke solution disclosed by Hollenbeck is not practical for coating a casing on a high speed production line to produce a coated casing which can then be shirred by conventional methods and used as a shirred casing on an automatic stuffing machine. The high viscosity of the Hollenbeck coating solution limits the casing coating speed and, if a conventional method such as "slugging", also called "bubble coating", is used to coat the inside of casing, the viscous Hollenbeck coating necessitates frequently cutting the casing open to replenish the slug of coating material within the casing, which results in short lengths of casing and thus makes continuous shirring impractical.
Heretofore, however, it has been found that providing casings which afford special treatment or structural characteristics to the food product can be more uniformly and economically accomplished by the casing manufacturer. This is especially true with the advent of, and wide commercial use of, automatic stuffing and processing equipment in the processed food industry.
Several methods of providing food casings with coatings applied to a surface thereof are known and described in the patent literature. There is disclosed, for example, in U.S. Pat. No. 3,451,827 a spraying method for applying a variety of coating materials over the internal surface of small diameter casings. In U.S. Pat. No. 3,378,379 to Shiner et al., a "slugging" method is used for applying coating materials to the internal surface of large diameter casings. While such techniques and others have been used in preparing commercial quantities of a variety of coated food casings, including casings where liquid smoke is employed as a component in the coating composition, the casings produced thereby have been designed to meet particular commercial requirements and, to the best of my knowledge, none of the prior art coated casings disclosed have been known to successfully impart a satisfactory level of "smoke" flavor and color to a meat product processed therein. For example, in U.S. Pat. No. 3,360,383 to Rose et al. and in U.S. Pat. Nos. 3,383,223 and 3,617,312 to Rose, there are disclosed coating compositions of various protein materials, such as gelatin, that employ liquid smoke solutions in amounts specifically required to insolubilize the protein materials. Such coated casings are disclosed as exhibiting special adhesion properties required for the processing of dry sausages, which properties would therefore limit the suitability thereof for many other casing applications.
The prior art patents teach application of liquid smoke to the internal surface of a casing, but attempts to internally coat the casing during the manufacture thereof have been found to be costly and to limit the speed of a continuous high speed production line.
One solution to this problem as described and claimed in copending United States application Ser. No. 062,358 filed July 3, 1979 in the name of Herman Shin-Gee Chiu, now abandoned, involves treating the external surface of the food casing with an aqueous liquid smoke composition derived from natural wood. Chiu also discovered that when the food casing is cellulosic and formed of either non-fibrous gel stock or fibrous gel stock, the use of highly acidic (pH of 2.0 to 2.5) aqueous liquid smoke results in the formation of a tarry deposit accumulating on the carrier rolls and the squeeze rolls of the smoke treatment unit, thereby eventually forcing shutdown of the treating system. It was discovered that this problem could be overcome by at least partially neutralizing the as-is liquid smoke to precipitate the tar, and then treating the cellulosic gel stock casing with the tar-depleted liquid smoke. Chiu discovered that contrary to the previous state-of-art belief, the tar-depleted liquid smoke, surprisingly, still possesses significant smoke coloring and flavoring capability, and this invention is described and claimed in his previously referenced United States application Ser. No. 417,171, "Tar-Depleted Liquid Smoke and Treated Food Casing", filed contemporaneously with this application.
One problem with the neutralization method of preparing the low tar aqueous liquid smoke composition of the last-mentioned Chiu application is that the coloration capability or "Staining Power" of the wood-derived liquid smoke declines with increasing pH or neutralization.
One object of this invention is to provide a method for preparing tar-depleted liquid smoke from a tar-containing wood-derived liquid smoke without requiring neutralization of the latter.
Another object of this invention is to provide a tar-depleted aqueous liquid smoke solution with high capability for imparting smoke color, odor and flavor to food products.
Still another object of this invention is to provide a tar-depleted, smoke colored and flavored tubular food casing with high capability for imparting smoke color, odor and flavor to food products encased therein, by treatment with the aforementioned solution in turn prepared by the aforementioned method.
A further object of this invention is to provide a method for preparing a smoke colored and smoke flavored foodstuff within the aforementioned tar-depleted, smoke colored and smoke flavored tubular food casing.
Other objects and advantages of the invention will become apparent from the ensuing disclosure and appended claims.